WIPED CLEAN – Using a baby wipe, Aaron Rollos shows how easily the black film that coats plants and objects around his Marstons Mills home comes off.

Common problem has banner year

It was something that Aaron and Julie Rollo didn’t pay much attention to, but when they started looking around their yard, their cars and other things in their Marstons Mills neighborhood, they knew something was up.

As regular walkers through their neighborhood just south of Race Lane with their 18-month-old daughter, Sophia, and two dogs, the Rollos noticed everything was turning black and collecting what they described as sediments or deposits.

“We didn’t notice it at first, but when we started looking it was everywhere,” Aaron Rollo said.

They first noticed it on their cars, but then took a closer look around the yard and it was on most everything, including the window sills.

The couple thought that it might be something carried in the air, and weren’t sure how concerned they should be.

“I’d never seen anything like it,” Julie Rollo said, saying that she’d been in the house seven years. Longer-term residents expressed the same thing to them.

“That’s when we knew something was different,” she said.”

What the Rollos and others in the Marstons Mills neighborhood are experiencing is a good crop of sooty mold.

That’s the conclusion of Cape Cod Extension Service education coordinator Roberta Clark and “Garden Lady” C.L. Fornari, based on photos provided by the Patriot.

According to literature from the Extension Service, “Sooty mold is a dark colored fungus that grows on honeydew excreted by piercing sucking insects or on substances exuded from leaves of certain plants.”

Clark provided a possible culprit.

“If there are oaks overhanging these plants, look for leucanium scale on the twigs,” she wrote in an e-mail to the Patriot. “It has been a banner years for this pest of oaks. It can be managed with oils but if the tree is large, a professional arborist would be advised.”

There are a number of oaks in the Rollos’ yard and throughout the neighborhood. As for its effect on humans, many people are allergic to sooty mold, according to the U.S. Forest Service, which notes, “particularly the Cladosporium and Aureobasidium components common in sooty molds of the Eastern U.S.”

According to both Clark and Fornari, the danger for plants is that the thickening black film can disrupt photosynthesis and stress the plant. While the mold is not damaging, the insects creating the excretions can be.

“The real problem isn't the mold, but the insects that cause it,” Fornari said, adding that to get rid of the mold, one has to get rid of the insects.

As for the cars, lawn furniture and other man-made materials, they are also susceptible to sooty mold if the same excretions fall on them.

“Sooty mold can grow on anything that is covered by the insect excretions,” Fornari wrote in an e-mail. “Because these excretions are high in plant sugars (the food the insects are living on!) they are sticky, so it's kind of like having a layer of glue fall on your boat, car etc. Then the back mold grows on it and it's very hard to get off.”

Fornari provided some reassurance that while it can bloom up, “sooty mold, and the insects that cause it, are always with us.

“I remember about 12 years ago noticing a yew in front of the hardware store in Osterville that was completely, totally black instead of green,” she wrote.